Figure 9.47.2.

Attenuation of Mxt-induced senescence in A549 cells by BRB as measured by cell morphometric features and expression of p21^WAF1 and rpS6^P. Exponentially growing cells were untreated (Ctrl) or treated with 2 nm Mxt in the absence or presence of 5 to 60 µM BRB for 5 days. (A) Bivariate distributions of nuclear area (DNA-DAPI) versus mean intensity of maximal pixels of DAPI fluorescence per cell. The ratio of maximal pixels to nuclear area (mp/A) is expressed as SI (i.e., relative to the same ratio in Ctrl cells). Note that SI is progressively reduced (in a dose-dependent manner) in BRB-treated cells relative to cells treated with Mxt alone. Arrows are percent increase in mp/A in BRB-treated cultures (i.e., percent reduction of SI) with respect to Mxt alone. (B) Bivariate distributions of p21^WAF1 and rpS6^P versus cellular DNA content. x is fold increase in mean expression for all cells with respect to Ctrl cells; arrows are percent reduction of expression in BRB-treated cultures compared to Mxt alone. Since aging and induction of premature senescence is considered to be driven by constitutive mTOR signaling, which converges on activation of rpS6 (Blagosklonny, 2008; Zoncu et al., 2011; Magnuson et al., 2012), potential anti-aging agents are expected to reduce the level of rpS6 phosphorylation.